The soybean GmPUB21-interacting protein GmDi19-5 responds to drought and salinity stresses via an ABA-dependent pathway

Drought-induced protein 19 (Di19) is a Cys2/His2 zinc-finger protein that functions in plant growth and development and in tolerance to abiotic stresses. GmPUB21, an E3 ubiquitin ligase, negatively regulates drought and salinity response in soybean. We identified potential interaction target proteins of GmPUB21 by yeast two-hybrid cDNA library screening, GmDi19-5 as a candidate. Bimolecular fluorescence complementation and glutathionine-S-transferase pull-down assays confirmed the interaction between GmDi19-5 and GmPUB21. GmDi19-5 was induced by NaCl, drought, and abscisic acid (ABA) treatments. GmDi19-5 was expressed in the cytoplasm and nucleus. GmDi19-5 overexpression conferred hypersensitivity to drought and high salinity, whereas GmDi19-5 silencing increased drought and salinity tolerance. Transcripts of ABA- and stress response-associated genes including GmRAB18 and GmDREB2A were down-regulated in GmDi19-5-overexpressing plants under drought and salinity stresses. ABA decreased the protein level of GmDi19-5 in vivo, whereas GmPUB21 increased the decrease of GmDi19-5 after exogenous ABA application. The accumulation of GmPUB21 was also inhibited by GmDi19-5. We conclude that GmPUB21 and GmDi19-5 collaborate to regulate drought and salinity tolerance via an ABA-dependent pathway.